I have two trailers, one a 5x8 mower trailer and the other a 16 foot car carrier I use for my tractor. Both have tires that are around 15 years old and both are stored out in the open where they get assaulted by UV and ozone daily. The difference in the tires is remarkable. The car carrier tires have plenty of tread but are deeply cracked and I just bought four new ones. The mower trailer tires on the other hand look like they were just installed yesterday. There’s not a crack or imperfection to be found on either of them. The difference in how well they have resisted cracking in the sun is hard to believe. I never would have thought there could be such a difference in UV resistance between brands of tires.